The present invention relates to an integral casting apparatus for use with a metallurgical vessel, such as a tundish, for the continuous casting of molten metal through a discharge opening thereof. More particularly, the present invention is directed to such an apparatus including means for preventing solidification in and around the discharge opening of the first portion or charge of molten metal at the beginning of a continuous casting cycle.
In continuous casting plants or arrangements, wherein molten metal is discharged through a nozzle or discharge opening of a metallurgical vessel such as a tundish, a critical problem involves the tendency of the first portion or charge of the molten metal to solidify on or around the nozzel or discharge opening. This is due to the fact that at the beginning of a continuous casting operation, the first portion or charge of the molten metal cools on the vessel walls and at the perforated brick defining the discharge opening, since initially such elements of the vessel are less hot than the molten metal. This results in a tendency of the molten metal to "freeze" in the nozzle.
One manner of avoiding this problem in the past has been to employ burners, such as gas burners, to preheat the nozzle or discharge opening area of the vessel. This however is very expensive and time consuming. Another past attempted solution to this problem is to position an overflow pipe in the vessel above the discharge opening. By this arrangement, the melt must reach a given bath height or level before it will be allowed to pass to the discharge opening. In other words, this arrangement is intended to provide an initial, relatively large first charge of molten metal to the discharge opening, rather than a more gradual initial discharge without the overflow pipe. It has been found however that this technique is insufficient to entirely solve the problem of solidification in the discharge opening.
Additionally, it is known in metallurgical arts that there are materials which may be added to molten metal to effect the flow characteristics thereof, i.e. to make the molten metal flow easier and to counteract the tendency thereof to solidify. However, such materials have not been employed in an arrangement to satisfactorily overcome the above discussed fundamental problem of solidification of the initial portion or charge of molten metal discharged through a discharge opening in an integral, continuous casting operation.